This is a request for the support of a project designed to test the hypothesis that CNS glutamatergic receptors composed of NR1 or GluR2 subunits are necessary for the behavioral adaptations that occur during repeated cocaine or opioid use and are manifest as drug reward and relapse as well as opioid tolerance and dependence. These studies will use the Cre-loxP technology to produce a knockout (KO) of the NMDAR1 (NMDA receptor) and/or GluR2 (AMPA receptor) subunits that is confined to selected CNS areas including the nucleus accumbens, ventral tegmental area and ventral subiculum (a spacial KO) in adult mice (a temporal KO). The spacial localization will result from the guided injection of a Cre expressing viral vector (recombinant AdenoAssociated virus) into the brain locus of interest in adult mice that have a mutation (IoxP sites) in the introns surrounding critical segments of the gene for the NR1 or the GluR2 subunit. The Cre-induced recombination will result in the localized deletion of the gene for the NR1 or the GluR2 subunit. Molecular and biochemical techniques including immunocytochemistry, in situ hybridization and electron microscopy, will be used to demonstrate the spacial localization and temporal characteristics of the changes in gene expression that are associated with the deletion of the targeted receptor subunits. Behavioral methods including sensitization, conditioned place preference and reinstatement of cocaine seeking behavior will be used to determine the effects of the targeted deletion of these receptor subunits in the selected CNS areas given above, on the behavioral adaptations to cocaine and opioid use including drug reward and relapse. This research will be supported by the core personnel and facilities of this Project and we will participate in the training activities of the Project.